玉米穗上多叶基因挖掘和生物学功能研究

Leaf number above ear (LNAE), one of the most important plant architecture traits for maize agronomics, plays a crucial role in determining photosynthesis and grain yield. We have developed four near-isogenic maize lines, designated as Y53-4L, Y53-8L, Y53-14L and Y53-16L, which contain four, eight, fourteen and sixteen leaves above ear, respectively. In addition, using different segregation populations derived from these near-isogenic lines, we detected two major QTLs for LNAE. In the present research project, we plan to expand the segregation populations and finely map the major QTLs for LNAE. Subsequently, we will clone the candidate genes for the major QTLs based on the fine mapping results, and investigate the functional properties of the candidate genes through genetic transformation way. Considering the fact that increased LNAE may increase plant height and/or delay mature time of maize, we also investigate the genetic interaction effect between LNAE and the other two traits, plant height and mature time. For this purpose, two LNAE near-isogenic lines, Y53-8L and Y53-4L, will be crossed with plant height near-isogenic lines for gene ZmGA3ox2, and mature time near-isogenic lines for gene Vgt1, resulting in different types of F1 hybrids for evaluating LNAE, plant height, mature time, and other important agronomic traits, including yield. Finally, we will develop leafy maize materials with either early mature time or short plant stature through marker-assisted selection methods. The results gained from this research project possess important theory and application value not only in enhancing the understanding of genetic architecture that regulates maize plant architecture, but also in developing maize hybrids with high yield in breeding practice.

穗上叶片数是玉米重要的株型性状，适当增加穗上叶片数有助于增大光合叶面积，提高产量。前期研究中，我们育成了含有4、8、14和16张穗上叶的一组近等基因系Y53-4L、Y53-8L、Y53-14L和Y53-16L，并鉴定出了2个穗上多叶主效QTL。本项目拟扩大分离群体，精细定位和克隆穗上多叶主效QTL，通过遗传转化确定候选基因的功能。考虑到穗上叶片数增加可能会同步增加株高和延长熟期，本项目还将利用穗上叶片数有差异的近等基因系，分别与另外二组在株高基因ZmGA3ox2和熟期调控基因Vgt1有差异的近等基因系杂交，调查杂种F1穗上叶片数、株高和生育期，研究三个位点不同等位基因间的互作效应，选择在穗上叶片数增加的情况下株高或熟期不变的最优等位基因组合。另外，利用分子标记选育早熟多叶型玉米和矮杆多叶型玉米种质材料。研究结果对于解析玉米株型形成的遗传调控网络和培育高产玉米品种具有重要理论意义和应用价值。

穗上叶片数是玉米重要的株型性状，适当增加穗上叶片数有助于增大光合叶面积，提高产量。本项目利用穗上多叶玉米自交系构建分离群体，精细定位穗上多叶基因，结合转录组数据，预测候选基因；利用具有不同穗上叶片数的玉米近等基因系，研究穗上多叶基因的生物学功能；利用具有不同穗上叶的近等基因系与熟期和/或株高存在差异的玉米骨干系杂交，研究穗上多叶基因与株高、熟期基因的互作效应，提出育种利用策略；并利用分子标记辅助选择方法创制穗上多叶玉米新材料。主要进展如下：（1）利用具有10张穗上叶自选系Y915和5张穗上叶自交系Z58杂交衍生的F2:3家系，在三个大田种植条件下检测到10个穗上叶片数QTL，其中两个QTL qLA3-4 和qLA7-1在不同环境中稳定表达，解释的表型变异分别为38.18~58.89%和10.32~20.32%，LOD值分别为20.57~39.47和7.58~10.01；进一步利用F3和F4分离大群体，将QTL qLA3-4 区间缩小至1.5M染色体区间。（2）将穗上多叶基因导入普通玉米自交系并构建成一对近等基因系，发现QTL qLA3-4能增加3张穗上叶，并能显著降低植株穗位高，提高粒重，但也同时增加株高和延长熟期。（3）利用RNA-Seq技术测定近等基因系的基因表达量，在QTL qLA3-4区间发现14个差异表达基因。（4）玉米穗上多叶自交系的产量配合力显著高于普通自交系，将穗上多叶基因、早熟基因和矮杆基因组合，可育成熟期早、株高适中的高产玉米杂交种。（5）通过分子标记辅助选择获得导入穗上多叶基因的稳定自交系2份、中间材料10份，育成通过省级审定的玉米新品种1个、后备青贮玉米组合2个。（6）为后续的穗上多叶基因图位克隆，用限制性内切酶HindIII构建了穗上多叶自交系Y915的基因组BAC文库，共有160个混合池，每个混合池至少包含1200个克隆，检测随机挑选的42个克隆的插入片段，平均长度约为143.4 kb，大约覆盖整个基因组11倍。（7）发表研究论文6篇，其中SCI论文4篇，培养硕士研究生5名。本项目获得的研究结果对于解析玉米株型形成的遗传网络和培育高产玉米新品种具有重要理论和应用价值。